[PATCH] perf python: Track linked libraries as extension dependencies

[James Clark <james.clark@linaro.org>]

Since the Python extension switched to linking perf libraries, setup.py
only lists util/python.c as a source. The libraries are supplied through
LDFLAGS, which setuptools does not consider when deciding whether the
extension needs to be rebuilt.

When a library changes, make invokes setup.py, but setuptools can skip
the build and the recipe copies the stale cached extension back into
python/. This leaves perf and its Python module running different
versions of the same code.

Pass the linked library paths to setup.py and declare them as Extension
dependencies so that library changes trigger a rebuild. Include
EXTRA_PERFLIBS in the shared library list so that both make and
setuptools track those inputs as well, preserving the existing linker
order.

Fixes: 9dabf4003423 ("perf python: Switch module to linking libraries from building source")
Assisted-by: Codex:GPT-6-Astra
Signed-off-by: James Clark <james.clark@linaro.org>
---
 tools/perf/Makefile.perf | 5 +++--
 tools/perf/util/setup.py | 1 +
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
index 7ceefc1da774..dbf7cceaa005 100644
--- a/tools/perf/Makefile.perf
+++ b/tools/perf/Makefile.perf
@@ -526,8 +526,8 @@ endif
 EXTLIBS := $(call filter-out,$(EXCLUDE_EXTLIBS),$(EXTLIBS))
 LIBS = -Wl,--whole-archive $(PERFLIBS) $(EXTRA_PERFLIBS) -Wl,--no-whole-archive -Wl,--start-group $(EXTLIBS) -Wl,--end-group
 
-PERFLIBS_PY := $(call filter-out,$(LIBPERF_BENCH) $(LIBPERF_TEST),$(PERFLIBS))
-LIBS_PY = -Wl,--whole-archive $(PERFLIBS_PY) $(EXTRA_PERFLIBS) -Wl,--no-whole-archive -Wl,--start-group $(EXTLIBS) -Wl,--end-group
+PERFLIBS_PY := $(call filter-out,$(LIBPERF_BENCH) $(LIBPERF_TEST),$(PERFLIBS)) $(EXTRA_PERFLIBS)
+LIBS_PY = -Wl,--whole-archive $(PERFLIBS_PY) -Wl,--no-whole-archive -Wl,--start-group $(EXTLIBS) -Wl,--end-group
 
 export INSTALL SHELL_PATH
 
@@ -559,6 +559,7 @@ $(shell [ -d '$(OUTPUT)python' ] || mkdir -p '$(OUTPUT)python')
 $(OUTPUT)python/perf$(PYTHON_EXTENSION_SUFFIX): util/python.c util/setup.py python/perf.pyi $(PERFLIBS_PY)
 	$(QUIET_GEN)LDSHARED="$(CC) -pthread -shared" \
         CFLAGS='$(CFLAGS)' LDFLAGS='$(LDFLAGS) $(LIBS_PY)' \
+	  PYTHON_EXT_DEPS='$(PERFLIBS_PY)' \
 	  $(PYTHON_WORD) util/setup.py \
 	  $(python_setup_quiet) build_ext; \
 	cp $(PYTHON_EXTBUILD_LIB)perf*.so $(OUTPUT)python/; \
diff --git a/tools/perf/util/setup.py b/tools/perf/util/setup.py
index 8380980ade4c..3b6a59f66944 100644
--- a/tools/perf/util/setup.py
+++ b/tools/perf/util/setup.py
@@ -173,6 +173,7 @@ def main() -> None:
     perf = Extension(
         'perf',
         sources=[os.path.join(src_perf, 'util/python.c')],
+        depends=shlex.split(os.getenv('PYTHON_EXT_DEPS', '')),
         include_dirs=['util/include'],
         extra_compile_args=cflags,
     )

---
base-commit: 705da5b15ab89ba97b11eedbe507c2fd83d31cb9
change-id: 20261001-james-perf-stale-python-build-d6b17da2f231

Best regards,
--  
James Clark <james.clark@linaro.org>